The article seems to be something of a joke. Yes, caster angle is important for stability, but the Gyrobike training wheel seems to illustrate how gyroscopic forces can also be helpful.
See: http://www.youtube.com/watch?v=Cbfe2_2DDc0
Additionally, stationary trainers like rollers that don't allow for the steerage correction described by the author illustrate how at speed something other than castor angle is assisting in stabilizing the bike.